fix pipefail and || precedence in content= pipeline

content=$(grep ...; grep -v ... ||: | grep -v ...) has two issues under set -euo
pipefail: (1) the first grep will exit non-zero when there are no Docker-
specific entries, which will abort the script; and (2) due to ||/| precedence,
the grep -v "^#" filter is not applied when the second grep -v succeeds. This
can break Docker builds in repos without docker/ entries in .tool-versions.

Author: cgitim

scripts/docker/docker.lib.sh

@@ -248,7 +248,7 @@ function _replace-image-latest-by-specific-version() {
 
   if [[ -f "$versions_file"  ]]; then
     # First, list the entries specific for Docker to take precedence, then the rest but exclude comments
-    content=$(grep " docker/" "$versions_file"; grep -v " docker/" "$versions_file" ||: | grep -v "^#")
+	content=$({ grep " docker/" "$versions_file" || true; grep -v " docker/" "$versions_file" || true; } | grep -v "^#" || true)
     echo "$content" | while IFS= read -r line; do
       [ -z "$line" ] && continue
       line=$(echo "$line" | sed "s/^#\s*//; s/\s*#.*$//" | sed "s;docker/;;")